This invention relates to an apparatus for applying liquid finish to a moving continuous filament yarn. More particularly, it relates to an improved groove-type finish applicator that provides uniform finish application to a moving continuous filament yarn with a capability to compensate for yarn misalignment in the slot.
U.S. Pat. No. 4,397,164 of common assignee discloses a yarn finish applicator in which finish is metered to a slot running from top to bottom of the applicator. The configuration of the body of the applicator and its slot provides an edge at the exit end of the applicator and a slot that is slightly wider at the location at which finish is metered to the slot than at exit of the slot.
The yarn finish applicator includes a body member that has top, opposed side, front and back surfaces. A slot with bottom and side walls is formed in the front surface running from top to bottom of the body member. The slot has bottom and side walls with a passage connecting the back surface of the body member through which is metered the desired quantity of liquid finish. The lower portion of the front and back surfaces of the body member are angled downwardly toward each other and in conjunction with the opposed side surfaces which taper downwardly toward each other form an adge at the bottom wall of the slot. The side walls of the slot taper inwardly toward the bottom wall while tapering toward each other from top to bottom. This unique slot configuration not only facilitates placing the moving yarn line in the applicator slot but also prevents the finish from migrating by surface-tension-induced spreading away from the yarn path.
In the apparatus disclosed in the above-noted patent, liquid finish is applied to the yarn through a passage 30 in the bottom wall 28 of the slot 20. When the threadline is aligned in the slot a uniform finish application to the threadline results. However, it has been found that the requirements to adapt these applicators to certain existing equipment are extremely difficult to implement and as a consequence, on occasion, threadline misalignment occurs with respect to the slot in the applicator resulting in less than the desired uniformity of finish application to the threadline passing through the applicator. This is particularly true when the threadline is moving at speeds greater than 3500 meters/minute and applying low finish levels, i.e. about 1%, to the threadline.